Cover Cropping Improves Soil Quality and Physical Properties

Introduction

Recent environmental concerns and ecological awareness have focused on a resurgence of cover crop use in sustainable agriculture. Cover crops improve soil physical, chemical and biological properties, supply nutrients to the succeeding crop, suppress weeds, increase soil structural stability, prevent erosion and break pest cycles. Some cover crops are able to break into compacted soil layers, making it easier for the succedding cash crops’ roots to develop more fully. However, the actual benefits from cover crops depend on the species and productivity of the crop to grow and the duration it is allowed to grow before the soil is prepared for the next crop (Anonymous, 2009).

Cover crops are planted between two main crops and are known to provide various ecological services in agio-ecosystems, such as protection against soil erosion, reduction of nutrient losses, improvement of soil and water quality, increase soil fertility and to some extent, the reduction of weeds and pests (Dabney et al„ 2001; Dom et al„ 2015; Wittwer et al., 2017). Furthermore, adding a legume species as a cover crop can improve N nutrition of the succeeding main crop and increase the soil N organic pool. Thus, cover crops can contribute to sustainable agriculture and alleviate weed and crop-nutrition issues related to both organic and conservation agriculture. Despite these advantages, cover crops are generally not widely used by producers, mainly due to seed availability, additional costs and labour requirements. Moreover, cover crop effects on productivity, crop nutrition and weed control are variable and depend on the cover-crop species, soil type and climate (Thorap-Kristensen et al., 2003; Wittwer et al., 2017).

The use of cover-crop cultivars and blends enhance soil quality by increasing biodiversity and efficiency (by providing food and energy resources) for soil-bome beneficial organisms, which in turn creates a balanced soil that resists degradation and responds to management practices in a predictable maimer (Sylvester and Bird, 2017). An illustration of how cover crops work is shown in Fig. 1.

Grass cover crops, such as lye, generally reduce nitrate-N loss, but the magnitude of the leaching reduction effect also varies widely across years, locations and management (Dabney et al., 2010; Diimes et al., 2002; Kaspar and Singer, 2011; Tliorup-Kristensen et al., 2003; Martinez-Feria et al., 2016). This indicates that lye effects on the maize system depend on specific combinations of management choices and environmental conditions. Most studies have focused on quantifying rye effects on final maize yields and/or annual nitrate-N losses but a knowledge gap still exists regarding the mechanisms by which lye affects these systems.

Tekndag Namik Kemal University, Tekirdag, Turkey.

How cover crops work? (Source

Fig. 1 How cover crops work? (Source: Sylvester and Bird, 2017).

A larger body of evidence exists for abiotic factors, which allow us to develop a generalised framework of the abiotic effects of lye on the maize system (Fig. 2; Martinez-Feria et al., 2016). Research findings have shown maize yield reductions following a lye cover crop, to be related to the depletion of soil moisture or suspected allelopathic effects. The collection of data dining years

A generalised diagram showing the abiotic mechanisms by which rye cover crop can affect crop yield and N losses in

Fig. 2 A generalised diagram showing the abiotic mechanisms by which rye cover crop can affect crop yield and N losses in

maize-based systems (Martinez-Feria et al., 2016).

in which crops experienced drought, flood and historically average weather, as well as included measurements of many system variables, are shown in Fig. 2 (Martinez-Feria et al„ 2016).

Each cover crop has a niche or special purpose and offers many benefits to producers that increase farm profitability and environmental sustainability. Legumes, as cover crops, are typically used to fix atmospheric N (produce homegrown nitrogen) biologically and increase soil fertility. Grass cover crops are used to increase soil organic matter (SOM), recycle excess nutrients and reduce soil compaction. Brassica crops are grown to loosen the soil, recycle nutrients and suppress weeds. Some other cover crops are grown to suppress insects, disease, weeds, or attract beneficial insects. Therefore, cover crops should be considered an integral part of any fanning system in order to efficiently utilise water, nutrients, improve soil biological, chemical and physical properties associated with soil quality to improve farm stability and profitability (Hoorman et al., 2009). In this chapter, we will focus more on soil physical properties as core indicators of soil quality as directly or indirectly influenced by cover crops.

 
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